Indigo dye.



UNITED STATES PATENT onnion.

INDIGO DYE.

Specification of Letters Patent.

Patented Dec. 19, 1905.

Application filed October 12, 1904. Serial No. 228,196.

To all whom it may concern:

Be it known that I, JOHN W. Fruits, of Winston Salem, county of Forsyth,State of North Carolina, have invented an Improvement in Indigo Dyes, ofwhich the following is a specification.

My invention has reference to indigo dyes, and consists of certainimprovements, which are fully set forth in the following specification.

In another application, Serial No. 227,098, and filed October 4:, 1904,I have described a method of dyeing textile material with reduced indigodyes and in connection therewith have specified the mixture of indigodye forming the subject-matter of this application.

Heretofore the results with indigo in the art of dyeing have been, ifapplied to cotton yarn or fabrics in a strong or concentrated reducedsolution and then oxidized by exposure to the air or otherwise, theindigo is oxidized on the fiber superficially, and hence crooks badlyand scours badly. If the dyeing is done by repeated dips in a dilutereduced solution or a succession of comparatively dilute solutions, theresult is much better as to fastness to rubbing and scouring; but it isimpossible to exhaust an ordinary indigo-vat entirely, and if the weakindigo solution be run off there is considerable waste. Further, veryserious practical difficulties are experienced in the effort to feedindigo, so as to keep up a standing vat. This is due to the fact thatthe reduced solution of indigo and the chemicals used for reduction areso unstable and are spontaneously decomposed, and, further, because thebath becomes saturated by these chemicalse. c with the salts of iron orlime, zinc, and soda.

I have found it advantageous to apply to the dry yarn or fabric areduced solution of indigo of such strength as is proportionate to theshade required by giving only one or two dips in this solution andexpressing the surplus dye by squeeze-rollers, an operation familiarlyknown as padding. For a full shade I prefer to use a padding liquorcontaining, for example, twenty pounds of indigo paste of twenty percent. strength, or four pounds of indigo-powder; twelve pounds ofunslaked lime,which is to be slaked in sufficient water and the milk oflime used; four pounds zinc-dust; two pounds caustic soda, solid orgranulated; two pounds starch, and two pounds alizarin-oil, seventy-fiveper cent, the whole made up to twelve and onequickness, and ease ofmanipulation.

half gallons with water of preferably 120 to 140 Fahrenheit. In thepreferred form of my composition I employ a mixture of the dryindigo-powder, zinc-dust, caustic soda, sifted lime, and starch,substantially in the proportions specified, which may be sold as acommercial compound and mixed with water for use. A solution thuscompounded will be found to go on or penetrate the fiber well; but ifexposed to the air, or if immersed in clear water, or in many solutionsthe indigo is oxidized on the fiber superficially. I convey the paddedyarn directly from the squeeze-rolls of this padding liquor into acompartment containingasolution which will prevent this oxidation, andthere the indigo is fixed upon or worked into the fiber, and the resultis a color much brighter and faster than can be obtained without thistreatment. Adilute solution of hydrosulfite of soda is efiicient forthis operation, or a solution of sodium sulfid may be used, which isstill cheaper and easier of application. Other solutions having areducing action or which will prevent the oxidation of the indigo duringthis operation may be substituted. After giving the yarn or fabric thedesired number of dips in this solution and passing through the propersqueeze-rolls the material is passed over reels in the air to oxidizethe indigo. It may then be rinsed or soaped, if desired, and dried. Allthese operations are preferably done in one continuous succession onmachines of simple construction.

While there are well-known ways of reducing indigo other than withzinc-dust and lime, I consider this the best because of cheapness,

Moreover, it appears to be the only manner of reducing indigowhichadmits of the ingredients being mixed together dry, if the alizarinoilbe left out; but in this case about four pounds of dry indigo-powdershould be used instead of the twenty pounds of paste, as stated in theformula.

Synthetic indigo is made .in a dry powder; but it is almost universallyused in the paste form, and it is recommended in this form by themanufacturers, because, as they say, the powder needs to be ground intoa paste with water before it can be properly used in making up anindigo-vat. The practical reason for this is that the dry powder issomewhat hard to mix with water in such fine subdivision and suspensionin the water as to get thorough reduction; but I have foundexperimentally that if it be intimately mixed with the otheringredients, especially the starch, there is no difficulty in holdingthem all in suspension in the water with complete and rapid reduction ofthe indigo. As far as I am aware this use of starch is new and original,and I have introduced it for the double purpose of giving body to thesolution to hold the other bodies in suspension until the indigo isreduced and also beis also to be understood that my invention includesthe use of the indigo either as a powder or as a paste, as may bedesired.

Having now described my invention, what I claim as new, and desire tosecure by Letters Patent, is-

1. A padding liquor for indigo dyeing which consists of a mixture ofindigo, milk of lime, zinc-dust, caustic soda, and starch, when mixedwith a solvent.

2. A padding liquor for indigo dyeing which consists of a mixture ofindigo, milk of lime, zinc-dust, caustic soda, starch, and alizarin,oil, when mixed with water to form a solution.

In testimony of which invention I have hereunto set my hand.

JOHN W. FRIES.

Witnesses: 7

(bus. A. WATSON, BERNARD J. PFOLEL.

